2-Acetylpyridine thiosemicarbazones. 1. A new class of potential antimalarial agents

Arylmethanol and thiosemicarbazone influence of plasmodial macromolecular synthesis and cell stability

The influence of mefloquine and additional antimalarial drugs on (3H)adenosine uptake, macromolecular synthesis, and cell stability was determined in rodent red cells parasitized with Plasmodium berghei. High arylmethanol to cell ratios induced lysis, whereas inhibition of macromolecular synthesis occurred at lower drug/cell ratios. A 2-acetylpyridine thiosemicarbazone rapidly suppressed (3H)adenosine uptake, and also blocked macromolecular synthesis by parasitized cells.

In vitro assessment of 2-acetylpyridine thiosemicarbazones against chloroquine-resistant Plasmodium falciparum

A series of 2-acylpyridine thiosemicarbazones was evaluated in vitro against a chloroquine-resistant Plasmodium falciparum strain. Antimalarial activity was assessed by the inhibition of uptake of [G-3H]hypoxanthine by the parasites. Among the mono- and disubstituted derivatives tested, 13 of 17 had 50% inhibitory doses of less than 10 ng/ml. Increasing the size of the ring at N4 from four to five, six, and seven members produced concomitant decreases in activity. Similarly, increasing the size of the aliphatic substituent on the azomethine carbon reduced activity. Selected compounds were also tested against a chloroquine-susceptible strain. The results suggested that the activities of these agents were not modified significantly by resistance to chloroquine. In general, in vitro activities correlate poorly with the in vivo activities in mice infected with Plasmodium berghei.

Antiviral activity of 2-acetylpyridine thiosemicarbazones against herpes simplex virus

2-Acetylpyridine thiosemicarbazone derivatives inhibited the replication of herpes simplex virus types 1 and 2 to a greater extent than cellular deoxyribonucleic acid or protein synthesis.

Preferential inhibition of ribonucleic acid synthesis by a new thiosemicarbazone possessing antibacterial and antiparasitic properties

We determined the influence of the azacycloheptane derivative (H) of a 2-acetylpyridine thiosemicarbazone on growth and macromolecular synthesis in Escherichia coli AT-9. Thiosemicarbazone H caused bacteriostasis and a primary inhibition of ribonucleic acid synthesis; secondary effects included inhibition of deoxyribonucleic acid and protein synthesis. Addition of cooper or other transition elements was not necessary for these inhibitions.

Activity of 2-acetylpyridine thiosemicarbazones against Trypanosoma rhodesiense in vitro

Twenty-seven 2-acetylpyridine thiosemicarbazones and analogs were tested for antitrypanosomal activity against Trypanosoma rhodesiense using a semiautomated in vitro assay system. Activity was determined by relative inhibition of uptake of two radiolabeled macromolecular precursors, [methyl-3H]thymidine and L-[U-14C]leucine, as compared to untreated controls. It was observed that the nitrogen atom of the pyridyl moiety of the 2-acetylpyridine thiosemicarbazones was essential for antitrypanosomal activity. The 2-acetylpyridine thiosemicarbazones generally inhibited the uptake of L-[U-14C]leucine to a greater extent than they inhibited [methyl-3H]thymidine uptake. Twenty-four of the 27 compounds tested exhibited activity comparable to that found for the antitrypanosomal agent ethidium bromide.

Inhibition of clinically significant bacterial organisms in vitro by 2-acetylpyridine thiosemicarbazones

Antibacterial activity of 65 2-acetylpyridine thiosemicarbazones and related compounds was determined by using clinical isolates of nine bacterial genera. Minimal inhibitory concentrations (MICs) of 0.002 to 0.062 micrograms/ml were obtained with 23% of the compounds for Neisseria gonorrhoeae and 0.016 to 0.062 micrograms/ml with 17% of the compounds for N. meningitidis. Staphylococcus aureus was inhibited in the MIC range of 0.125 to 0.5 micrograms/ml by 18% of the thiosemicarbazones, whereas 26% inhibited group D enterococcus with an MIC of 0.25 to 2.0 micrograms/ml. Poor antibacterial activity was shown toward the gram-negative bacilli, i.e., Pseudomonas, Klebsiella-Enterobacter, Shigella, Escherichia coli, and Proteus.